My experience is that if you don't have a number, the coaches will ACT as if you made it up.
I had a person work with me this year who didn't have a number on a foul in a varsity game. I was the WH. The coach wasn't thrilled. At halftime, I reminded everyone to be extra careful and get a number. You would've thought I asked some on the crew to cure some major disease. "It's a courtesy, " I was told. Easy for a back judge to say -- he isn't a wing or a WH getting chewed on for it
Rich